Charge forming device



Nov. 24,v 1931. F. E. ASELTINE CHARGE FORMING DEVICE Filed June 20, 1928uw sw atented Nov. 24, 1931 UNITED STATES PATENT OFFICE Tann n ASELTINE,OF DAYTON, OHIO, AssIeNOa, BY MEsNE ASSIGNMENTS, To DELCO PRODUCTSCORPORATION, or DAYTON, OHIO, A CORPORATION OE DELAWARE CHARGE FORMINGDEVICE Application led June 20,

This invention relates to charge forming devices for internalcom'bustion engines and more particularly to the type of charge formingdevice comprising a plurality of primary fuel mixing chambers, one foreach engine intake port and cooperating respectively With a plurality ofsecondary mixing chambers, each located adjacent an engine intake portand receivin fuel air mixture from a pipe connected with one of theprimary mixing chambers and receiving air, when required, through onebranch of an air manifold which supplies air to all of the secondarymixinfr chambers, the quantity of fluid flowing through the secondarymixing chambers being controlled primarily by a single main airthrottle. Fuel is conveyed to the primary mixing chambers through asingle fuel duct leading from` a common float bowl.

Examples of charge forming devices of this character are disclosed inthe applications of Wilford H. Tester, Serial No. 221,- 372, filedSeptember 22, 1927, and Fred E.

' Aseltine, Serial No. 288,684, led June 27,

n the devices disclosed in the above mentioned applications variousmeans are provided to control the proportions of fuel and' air in themixture, and in the second of these applications, each primary mixturepassage is provided with two fuel jets of different capacities, thesmaller of which is designed to supply fuel for idling and low speedoperations under load', while the larger jet is rendered effective onhigher engine speeds to supply the proper amount of fuel to the mixturewhen the capacity of the smaller jet is no longer sufficient to supplythe fuel necessary to form a mixture of properly combustibleproportions. Both of these fuel jets are anterior to the throttle andthe arrangement has not produced altogether satisfactory results. Theproportions of fuel and air in the mixture formed for idling and lowspeed operation under load' are not entirely correct during both ofthese operations.

It is, therefore, the principal object of the present invention toprovide a charge form- 1928. Serial No. 286,977.

ing device having means for forming a mixture of the desired proportionswhen the engine is idling, and under all Operating conditions and allspeeds when the engine is operating under load.

A more specific Obj ect of the invention is to provide novel means forsupplying a fuel mixture during idling, and more particularly to providesuch means in a device having a lurality of successively operated lowand gh speed jets, so constructed that the fuel supply means supplyingfuel for idling will not interfere with nor disturb the mixtureproportions in the mixture formed. when the engine is under load.

These objects are accomplished according to the present invention, bythe provision of a third fuel jet in each primary mixture passagecommunicating with said passage at a point posterior to the throttle.This fuel jet is vented to atmosphere so that it supplies a fuel mixtureof proper proportions for idling when the throttle is closed. As thethrottle is opened for Operation under load the suction at the idling-jet is reduced, the percentage of fuel in the mixture is reduced and byproperly proportioning the size of the fuel and air passages leading tothe idling jet, said jet can be made to cease functioning entirely whenthe other jets in the primary mixture passages begin to function.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings, wherein a preferred form of embodiment of the presentinvention is clearly shown.

In the drawings:

Fig. l is a section through the carburetor unit and the middle outletbranch of the manifold associated therewith, on the line 1-1 of Fig. 2.

Fig. 2 is a section on the line 2-2 of Fig. 1.

Fig. 3 is a section on the line 3-3 of Fig. 1.

The device disclosed herein comprises a main air manifold indicated inits entirety by the reference numeral 10, and having three outletbranches, the middle one of which 12 carburetor unit may be secured isprovided adjacent the manifold inlet.

The carburetor unit comprises a main housf ing 20 having an attachingflange 22 secured by' screws 24 to the flange 18. An. air inlet horn 26is secured by screws 28 to the main housing and communicates with anopening in the top wall of said housing. A casting 30 havin certain fuelpassages and a dash-pot cylin er formed therein is secured by screws 32to the bottom of the main housing, and a sheet metal fuel bowl 34 isheld tight against an annular shoulder 36 formed on a skirt 38 dependingfrom the main housing, by a screw 40 screwed into the casting 30, asuitable gasket being provided to prevent leakage around the screw.

Fuel is conducted from a main source of supply to the fuel bowl and theflow is control ed by a oat, (not shown) in the usual manner to maintaina constant level in the bowl. To convey fuel from the bowl to aplurality of primary mixture passages 42 hereinafter more fullydescribed, a vertical fuel assage 44 is provided in the casting 30.

he passage 44 connects, at its upper end, with a horizontal fuel canal46, and said canal communicates with three pairs of calibrated low andhigh speed jets or plugs 56 and 58 respectively, each of these pairs ofjets being adapted to convey fuel to one of the mixture passages 42 in amanner later described.

Fuel is lifted from the fuel bowl to the primary mixture passages by thesuction therein. When the throttle is moved toward closed position toreduce the engine speed, this suction may be reduced suiciently to allowthe fuel column between the bowl and the jets to drop enough totemporarily starve the engine unless means were provided to prevent t isaction. To revent this action, a check valve 60 is provi ed,which isnormally lifted above an annular rim 62, surroundmg the outlet ofpassage 44, by the suction, but on reduction of suction immediatelyseats on said rim preventing downward flow through the passage 44. A twostage metering valve 64 of the type shown in the above mentionedapplications, and operating in the same way,

` is provided in the passage 44.

The primary mixture passages 42 to which the pairs of jets 56 and 58deliver fuel are bored horizontally through the central part of the mainhouslng 20, are parallel to each other and relatively close together, asindicated in the drawings. Air is admitted to each of the primarymixture passages through an air inlet bushing 66 screwed into sage. Eachof the Venturi tu with two external ribs 72 arrange circumferentially ofthe tube and fitting ti htly in the enlargement 70. These ribs formtween them a fuel channel 74 with which the low speed jet 56communicates, and a series of orifices 76 are provided in the Venturitube to connect the interior of the tube with the said channel.

The Venturi tube 68 is reduced in size at its inner end and is spacedfrom the wall of the mixture passage, as shown in Fig. 1. This space 78is substantially a dead air space in which the suction or partial vacuumis substantially the same as that maintained in the mixture passagebetween the end of the Venturi tube and the throttle, which controlsflow through the mixture passage and is more fully describedhereinafter. Each main fuel nozzle 58 terminates in the wall of themixture passage 42 with which it is associated at a point opposite thereduced inner end of the venturi so that fuel flows therefrom into thespace 78 and the suction in said space controls the iiow of fuel; Itwill beclear that the suction within the Venturi tube 68, which iseffective to cause a flow of fuel through the low speed jet 56 andorifices 76 communicating therewith, is greater than that effective tocause a flow through the jet 58. Hence each jet 56 is effective tosup lyfuel to its associated mixture passage at ow speed when the suction inthe mixture passage is relatively low, while the main or high lll) mainor high speed jets are not effective to f supply any fuel to the mixturepassages until the engine is running at a speed correspondingsubstantially to a vehicular speed of 20-25 miles per hour. Theoperation and construction of the fuel jets is more fully described inmy copending application Serial No. 288,684, filed June 27, 1928, inwhich such structure is claimed.

The fiow of the primary mixture through the passages 42 is controlled bya single throttle valve 80, which extends across all of the passages 42and has grooves 82 therein which register with said passages. The meansfor operating this throttle forms no part of the present invention, butis fully disclosed in the application of W. H. Teeter referred toherein. Each primary mixture passage communicates with a pipe associatedwith each branch of the manifold for conveying the primary mixture tothe secondary mixing chambers. The pipe 84 associated with the middleoutlet branch 12 of the manifold is shown herein and those which conveyprimary mixture to the other branches of the manifold are fully shownand described in the above -mentioned applications, such structureforming no part of the present invention.

All of the air which is mixed with the primary mixture in the secondarycarburetors is admitted through the air horn 26, the flow beingcontrolled by an air valve 86, normally held against a seat 88 by aspring 90. Air passing the valve flows first into an air chamber 92 andthence through a secondary air passage 94 communicating with the inletend of the air manifold and provided with a throttle valve 96 secured toa shaft 98v journalled in the housing 20, and operated'in a' mannerbrieiy described hereinafter to regulate the How of air to the secondarymixmg chambers,

The spring 90 is received between the air valve and a flange 100projecting from a sleeve 102, slidable on a guide sleeve 104 whichguides the aii` valve stem in the manner described in the abovementioned application of W. H. Teeter.

The choke mechanism, which is not shown herein, is adapted to beoperated to lift the flange fully to bring sleeve 102 into engagementwith the air valve to hold said valve closed to facilitate starting, orartially to increase the tension of the sprmg holding the air valveclosed. To prevent suii'icient opening of the air valve to causeleaningr of the mixture and to prevent fluttering of said valve, adash-pot 106 is provided which may be of the form shown in either of thecopending cases referred to, or may be of any conventional or desireddesign. The throttle operating mechanism forms no part of this inventionand is not shown herein, but for the purpose of facilitatingunderstanding of the operation of thewhole device, the mode of operationof the throttles 80 and 96 will be very briefly described. Duringoperation at all speeds up to a vehicular speed of 20-25 miles per hour,it is desirable that the primary mixture passages supply all thecombustible mixture to the engine cylinders, and at speeds higher thanthat, to admit air to the secondary lmixing chambers through the passage94. To secure this result, the two throttles 80 and 96 are provided witha common operating mechanism so arranged that the primary throttle 80 isgiven a predetermined movement before the throttle 96 begins to open andafter said throttle 96 begins to open both throttles move together towide open position. j

There are three secondary mixing chambers of identical construction,each of which comprises a Venturi tube 110 secured in an outlet branchof the manifold in such position that its point of greatest depressionis immediately adjacent the outlet end of the primary mixture pipeassociated with that particular manifold branch, as shown in Fig. 1.`Each venturi is provided with an external circumferential rib 112which, when the device is assembled, is adapted to be clamped betweenshoulders 114 and 116 on the manifold and engine block respectively. The

Venturi tubes cause the air passing the ends of the primary mixturedelivery pipes to move at high velocity creating in each tube a highsuction during all operating conditions.

The above described mechanism is all old in my copending applicationabove referred to, but in that application the primary throttleoperating mechanism is designed to be slightly open at idling and thelow speed jets 56 supply lthe idling fuel, while. according to thepresent invention, the primary throttle is designed to be substantiallyclosed at idling and means have been added t'o the structure abovedescribed to supply fuel for idling. This means comprises a tube 120adapted to be4 secured in a recess 122 in the Wall of the main housingin. any suitable manner. This tube is long enough to extend below thelevel of the fuel in the bowl 34 and communicates at it's upper end witha passage 124 drilled in the housing. wall and of the same diameter asthe inside of tube 120. The passage 124 connects with a horizontalpassage 126 of greater diameter which is connected with all of theprimary mixture passage 42 by means of three identical vverticalpassages 128 forming idling jets, as

shown in Fig. 3. Air is admitted to the passage 124 from the atmosphereby means of a passage 130 .which extends through the attaching flanges18 and 22. The air admitted through this passage forms an emulsion orvery rich mixture of fuel and air which is drawn into the primarymixture passages by the high suction therein when'y the throttle isclosed. Any opening movement of the throttle which will bring either ofthe jets 56 or 58 into action may either reduce the flow of fuel fromthe idling ljets or cause such flow to cease entirely, depending on therelative sizes of the passages 124 and 130. It will be clear that thesuction elfective on the fuel tubes 120 is highest at "closed throttleand such suction is reduced by the admission of air through the passage130, the larger the passage 130 the v greater the reduction in suction.The parts may be so proportioned that the suction effective on the fueltube 120 is just enough, when the throttle 80 is closed, to lift fuelfrom said tube into the air stream flowing inwardly through passages 130and 124, so that, on any opening movement of the throttlethe suctioneffective on the fuel tube becomes too low to lift the fuel from thebowl to the top of tube 120 and the jets 128 cease to function.

On the other hand, the parts may be so proportioned thatI insuificientair is admitted through passage 130 to reduce the suction effective onthe tube 120 to a point Where such suction will fail to lift fuel fromthe bowl into the stream of air owing inwardly through the passage 130.If the parts are so proportioned the supply of rich mixture through thejets 128 will never cease, but will be gradually reduced as the throttleis opened. Either ofl these constructions, which differ only in theproportioning nf the parts may be provided Without depart-` ing from thespirit of this invention.

While the form of embodiment of the present invention vas hereindisclosed, constitutes a preferred form, it is to be understood thatother forms might be adopted, all coming within the scope of the claimswhich follow.

What is claimed is as follows; 1. A charge formingdevice for internalcombustion engines comprising mixing chamber, a primary mixing chamberfor supplying fuel mixture thereto, a main air passage supplying air tosaid secondary mixing chamber, a throttle controlling the primarymixture passage, a. normally closed valve controlling the ow of airthrough the main air passage and adapted to be opened during the openingmovement of said throttle, means for supplying fuel to the primarmixture passage comprlsing an idling jet e fective to supply fuel'before opening of the primary throttle, a low speed jet adapted tosupply fuel subsequentA to the',l opening of the primary throttle, and ahigh speed jet adapted to supply fuel after theqopening of the airthrottle.

2. A charge forming device-for internal combustion engines comprising aplurality of primary carburetors adapted to su ply fuel air mixture to aplurality of secondary mixing chambers, one of which is associated witheach engine intake port, means for admitting air and fuel to eachprimary carburetor, a throttle regulating the iiow therev through, aplurality of idling jets each of which supplies fuel to one of saidprimary carburetors, and a common fuel supply passage leading to allsaid idling jets.

3. A charge forming device for internal combustion engines comprising aplurality of primary carburetors adapted to su ply fuel airmixture to aplurality of secondary mixing chambers one of which is associated witheach engine intake port, means for admitting air and fuel to eachprimary carburetor, -a

throttle regulating the flow therethrough, a plurality of idling jets,each of which supplies fuel to one of said primary carburetors, a commonfuel supply passage leading to all vof said idling jets and meansadmittlng air to said supply passage.

4. A charge forming device for internal combustion engines comprising aplurality of primary carburetors adapted to su ply fuel air mixture to aplurality of secon ary mix- FRED E. ASELTINE.

a secondary

